A furnace, in particular for an electro thermal atomization device of an atom absorption spectrometer, has a heatable heat duct in which is mounted a trial platform. The incompatible filler provides domains in the polyester matrix, each domain having a particular dimension, thus providing a range of dimensions for the domains in the article. A flow opening is provided between the adjacent longitudinal walls of the outlet header of the one heat exchanger and the inlet header of the second heat exchanger.